An indicator of the size of the effect from using the intervention. It is the expected change in percentile rank for an average comparison group student if the student had received the intervention, ranging from -50 to +50. At the study level, the improvement index is only shown if the findings are characterized as statistically significant or substantively important (greater than +10 or less than -10); dashes are displayed for an indeterminate effect.

The name and version of the document used to guide the review of the study.

The version of the WWC design standards used to guide the review of the study.

The result of the WWC assessment of the study. The rating is based on the strength of
evidence of the effectiveness of the intervention. Studies are given a rating of
Meets WWC Design Standards without Reservations, Meets WWC Design Standards with Reservations,
or >Does Not Meet WWC Design Standards.

A related publication that was reviewed alongside the main study of interest.

Study findings for this report.

Based on the direction, magnitude, and statistical significance of the findings within a domain, the WWC characterizes the findings from a study as one of the following: statistically significant positive effects, substantively important positive effects, indeterminate effects, substantively important negative effects, and statistically significant negative effects. For more, please see the WWC Handbook.

The WWC may review studies for multiple purposes, including different reports and re-reviews using updated standards. Each WWC review of this study is listed in the dropdown. Details on any review may be accessed by making a selection from the drop down list.